Activation of the Two-Component System LisRK Promotes Cell Adhesion and High Ampicillin Tolerance in Listeria monocytogenes.

Listeria monocytogenes is a foodborne pathogen which can survive in harsh environmental conditions. It responds to external stimuli through an array of two-component systems (TCS) that sense external cues. Several TCS, including LisRK, have been linked to Listeria's ability to grow at slightly elevated antibiotic levels. The aim of this study was to determine if the TCS LisRK is also involved in acquiring the high antibiotic tolerance that is characteristic of persister cells. LisRK activates a response that leads to remodeling of the cell envelope, and we therefore hypothesized that activation of LisRK could also increase in the cells' adhesiveness and initiate the first step in biofilm formation. We used a ΔlisR mutant to study antibiotic tolerance in the presence and absence of LisRK, and a GFP reporter strain to visualize the activation of LisRK in L. monocytogenes LO28 at a single-cell level. LisRK was activated in most cells in stationary phase cultures. Antimicrobial susceptibility tests showed that LisRK was required for the generation of ampicillin tolerance under these conditions. The wildtype strain tolerated exposure to ampicillin at 1,000 × inhibitory levels for 24 h, and the fraction of surviving cells was 20,000-fold higher in the wildtype strain compared to the ΔlisR mutant. The same protection was not offered to other antibiotics (vancomycin, gentamicin, tetracycline), and the mechanism for antibiotic tolerance is thus highly specific. Furthermore, quantification of bacterial attachment rates and attachment force also revealed that the absence of a functional LisRK rendered the cells less adhesive. Hence, LisRK TCS promotes multiple protective mechanisms simultaneously.

Toxoplasma gondii, a Foodborne Pathogen in the Swine Production Chain from a European Perspective.

Toxoplasmosis is a foodborne zoonosis transmitted by Toxoplasma gondii, a cosmopolitan protozoan that infects humans through exposure to different parasite stages, in particular by ingestion of tissue cysts or tachyzoites contained in meat, primary offal (viscera), and meat-derived products or ingestion of environmental sporulated oocysts in contaminated food or water. The pig is an important species for infection: raw or undercooked pork consumption not subject to treatment able to inactivate the parasite represents a risk to consumers' health. Broadening knowledge of transmission ways and prevalence concerning this important pathogen in swine, together with a thorough acquaintance with hazard management are key elements to avoid T. gondii spreading within the swine production chain. This review aims to illustrate why toxoplasmosis should be regarded as a veterinary public health issue through a careful description of the parasite, routes of infection, and inactivation treatments, highlighting the main prevention lines from pig breeding to pork consumption.

Zoonotic parasites in feces and fur of stray and private dogs from Italy.

The present study evaluated the occurrence of zoonotic parasites in feces and on fur of stray and private dogs living in Italy. Individual fecal samples collected from 117 and 385 kenneled (i.e., rescue shelter) and privately owned dogs, respectively, were examined by conventional copromicroscopy. Samples positive for Giardia duodenalis and Cryptosporidium spp. were subjected to further genetic characterization. Additionally, 174 fur samples of private and kenneled dogs living in the same area, 27 of which were also subjected to copromicroscopical examinations, were examined for the presence and viability of parasite elements. Out of 502 fecal samples, forty-one (8.2%) scored positive for G. duodenalis cysts while one (0.2%) for Cryptosporidium oocysts. Nine private dogs were molecularly positive for G. duodenalis assemblage C (n. 7), assemblage D (n. 1), and assemblages C + D (n. 1), while 11 kenneled dogs were positive for assemblage C (n. 8), assemblage D (n. 1), and assemblages C + D (n. 2). Cryptosporidium spp. were identified as C. canis in a private dog. One hundred and seventy-two dogs (34.3%), i.e., 92 private and 80 kenneled, were positive for zoonotic nematodes: Toxocara canis (6.6 %), Ancylostoma caninum (6.8%), and Capillaria aerophila (0.6%). Unviable eggs of Toxocara spp. were found on the hair of five (2.9%) private dogs. The present findings indicate that canine feces from both private and kenneled animals may contain zoonotic parasites and may be a potential risk for humans and other animals, especially when they contaminate the environment. The role of dog fur as source of human infections should be further investigated.